Showing papers on "Memistor published in 2010"

Nanoscale Memristor Device as Synapse in Neuromorphic Systems

Abstract: A memristor is a two-terminal electronic device whose conductance can be precisely modulated by charge or flux through it. Here we experimentally demonstrate a nanoscale silicon-based memristor device and show that a hybrid system composed of complementary metal−oxide semiconductor neurons and memristor synapses can support important synaptic functions such as spike timing dependent plasticity. Using memristors as synapses in neuromorphic circuits can potentially offer both high connectivity and high density required for efficient computing.

‘Memristive’ switches enable ‘stateful’ logic operations via material implication

Abstract: The authors of the International Technology Roadmap for Semiconductors-the industry consensus set of goals established for advancing silicon integrated circuit technology-have challenged the computing research community to find new physical state variables (other than charge or voltage), new devices, and new architectures that offer memory and logic functions beyond those available with standard transistors. Recently, ultra-dense resistive memory arrays built from various two-terminal semiconductor or insulator thin film devices have been demonstrated. Among these, bipolar voltage-actuated switches have been identified as physical realizations of 'memristors' or memristive devices, combining the electrical properties of a memory element and a resistor. Such devices were first hypothesized by Chua in 1971 (ref. 15), and are characterized by one or more state variables that define the resistance of the switch depending upon its voltage history. Here we show that this family of nonlinear dynamical memory devices can also be used for logic operations: we demonstrate that they can execute material implication (IMP), which is a fundamental Boolean logic operation on two variables p and q such that pIMPq is equivalent to (NOTp)ORq. Incorporated within an appropriate circuit, memristive switches can thus perform 'stateful' logic operations for which the same devices serve simultaneously as gates (logic) and latches (memory) that use resistance instead of voltage or charge as the physical state variable.

Practical Approach to Programmable Analog Circuits With Memristors

Abstract: We suggest an approach to use memristors (resistors with memory) in programmable analog circuits. Our idea consists in a circuit design in which low voltages are applied to memristors during their operation as analog circuit elements and high voltages are used to program the memristor's states. This way, as it was demonstrated in recent experiments, the state of memristors does not essentially change during analog mode operation. As an example of our approach, we have built several programmable analog circuits demonstrating memristor-based programming of threshold, gain and frequency. In these circuits the role of memristor is played by a memristor emulator developed by us.

Implementing memristor based chaotic circuits

Abstract: This paper provides a practical implementation of a memristor based chaotic circuit. We realize a memristor using off-the-shelf components and then construct the memristor along with the associated chaotic circuit on a breadboard. The goal is to construct a physical chaotic circuit that employs the four fundamental circuit elements — the resistor, capacitor, inductor and the memristor. The central concept behind the memristor circuit is to use an analog integrator to obtain the electric flux across the memristor and then use the flux to obtain the memristor's characterstic function.

The fourth element: characteristics, modelling and electromagnetic theory of the memristor

Abstract: In 2008, researchers at the HewlettPackard (HP) laboratories published a paper in Nature reporting the development of a new basic circuit element that completes the missing link between charge and ...

Memristor-based multilevel memory

Abstract: A method to utilize the memristor as a multilevel memory has been proposed. There are several roadblocks in the practical use of memristors for multilevel memory. A difficulty comes from the nonlinearity in the ? vs. q curve which makes it difficult to determine the proper pulse width for desired resistance values. Another one comes from the property of the memristor which integrates any kind of signals including noise that appeared at the memristor and causes memristors to be perturbed from their original values. The proposed method enables the memristor to be used as multilevel memory using a reference resistance array by forcing the memristor to stick at a set of predetermined fixed reference resistance values. We propose the write-in (programming) circuit and the readout/restoration circuit which share the information storing technique using the reference resistance array.

General spice models for memristor and application to circuit simulation of memristor-based synapses and memory cells ¤

Abstract: Memristor had been first theorized nearly 40 years ago by Prof. Chua, as the fourth fundamental circuit element beside the three existing elements (Resistor, Capacitor and Inductor) but because no one has succeeded in building a memristor, it has long remained a theoretical element. Some months ago, Hewlett-Packard (hp) announced it created a memristor using a TiO2/TiO2-X structure. In this paper, the characteristics, structures and relations for the invented hp's memristor are briefly reviewed and then two general SPICE models for the charge-controlled and flux-controlled memristors are introduced for the first time. By adjusting the model parameters to the hp's memristor characteristics some circuit properties of the device are studied and then two important memristor applications as the memory cell in a nonvolatile-RAM structure and as the synapse in an artificial neural network are studied. By utilizing the introduced models and designing the appropriate circuits for two most important applications; a nonvolatile memory structure and a programmable logic gate, circuit simulations are done and the results are presented.

Design considerations for variation tolerant multilevel CMOS/Nano memristor memory

Abstract: With technology migration into nano and molecular scales several hybrid CMOS/nano logic and memory architectures have been proposed thus far that aim to achieve high device density with low power consumption. The discovery of the memristor has further enabled the realization of denser nanoscale logic and memory systems. This work describes the design of such a multilevel memristor memory (MLMM) system, and the design constraints imposed in the realization of such a memory. In particular, the limitations on load, bank size, number of bits achievable per device, placed by the required noise margin (NM) for accurately reading the data stored in a device are analyzed.

Hybrid CMOS/memristor circuits

Abstract: This is a brief review of recent work on the prospective hybrid CMOS/memristor circuits. Such hybrids combine the flexibility, reliability and high functionality of the CMOS subsystem with very high density of nanoscale thin film resistance switching devices operating on different physical principles. Simulation and initial experimental results demonstrate that performance of CMOS/memristor circuits for several important applications is well beyond scaling limits of conventional VLSI paradigm.

A memristor SPICE model for designing memristor circuits

Abstract: The memristor, a circuit element, was first presented by Leon Chua in 1971. The physical implementation of the memristor was created by scientists at HP Labs in 2008 and the coupled variable resistor model was proposed. Here we show a SPICE model for such a memristor using dependent voltage sources. The model is validated by simulating simple circuits and comparing with the expected results. The proposed model makes it possible to design and simulate memristor circuits using SPICE. We simulate two circuits, a low pass filter in which a memristor is in series with a resistor and an integrator circuit with operational amplifier. The results are compared with inductor circuits in which a memristor is replaced by an inductor. The comparison shows that a memristor is acting like an inductor under certain conditions. Since the memristor has great performance in terms of power dissipation and with its nanometer size there might be a possible application of the memristor to be used as an inductor.

A review on memristive devices and applications

Abstract: Recent discovery of the memristor has sparked a new wave of enthusiasm and optimism in revolutionising circuit design, marking a new era for the advancement of neuromorphic and analogue applications. In this work, we consider practical applications in which the highly non-linear dynamic response of the memristor can be employed. It is shown that the device can be utilised as a non-volatile memory element and/or a programmable dynamic load, with particular emphasis given into bio-inspired analog implementations that typically exploit the ability of the memristor to support both logic and memory simultaneously. Finally, a novel concept is presented demonstrating the capacity of memristive networks in realising demanding image processing algorithms and more specifically edge detection.

Compact method for modeling and simulation of memristor devices: ion conductor chalcogenide-based memristor devices

Abstract: A compact model and simulation methodology for chalcogenide based memristor devices is proposed. From a microprocessor design view point, it is important to be able to simulate large numbers of devices within the integrated circuit architecture in order to speed up reliably the development process. Ideally, device models would accurately describe the characteristic device behavior and would be represented by single-valued equations without requiring the need for recursive or numerically intensive solutions. With this in mind, we have developed an empirical chalcogenide compact memristor model that accurately describes all regions of operations of memristor devices employing single-valued equations.

Spintronic memristor devices and application

Abstract: Spintronic memristor devices based upon spin torque induced magnetization motion are presented and potential application examples are given. The structure and material of these proposed spin torque memristors are based upon existing (and/or commercialized) magnetic devices and can be easily integrated on top of a CMOS. This provides better controllability and flexibility to realize the promises of nanoscale memristors. Utilizing its unique device behavior, the paper explores spintronic memristor potential applications in multibit data storage and logic, novel sensing scheme, power management and information security.

Memristor-based arithmetic

Abstract: This paper describes strategies for performing arithmetic operations in memristor-based structures An overview of both analog and digital approaches offered in the literature for addition and multiplication will be described Memristor-based designs of an adder and a multiplier are presented

Low-power dual-element memristor based memory design

Abstract: Recently, the emerging memristor device technology has attracted significant research interests due to its distinctive hysteresis characteristic, which potentially can enable novel circuit designs for future VLSI circuits. In particular, characteristics such as non-volatility, non-linearity, low power consumption, and good scalability make memristor one of the most promising emerging memory technologies. Some important design parameter, however, such as speed, energy consumption, and distingushiablility, are mainly determined by the memristor's physical characteristics. In this paper, a key observation of memristor's asymmetric energy consumption is made by the detailed analysis of the transient power consumption. Based on this observation, we propose a dual-element memory structure in which each memory cell consists of two memristors. By constantly writing complement bits into the two elements within a cell, the dual-element is flexible to satisfy design constraints which are usually difficult to be satisfied with one-cell memory structure. Design space of the dual-element memory cell is studied and it shows that the trade-offs among the energy, speed, and distingushiablility should be explored for different design objectives. In particular, we show that under the energy-driven optimization, the proposed dual-element memory achieves the same programming speed and distinguishability as conventional single-element memory but the energy consumption can be reduced by up to 80%.

Arithmetic operations within memristor-based analog memory

Abstract: This paper describes how memristors could be used as an analog memory and computing elements. The key idea is to apply comparison and programming phases cyclically so that the memristor can be programmed to a given conductance level at a fixed voltage. It is further described how the cyclical programming could be used in computing. A configuration needed to copy the sum of conductances of two memristors into a third one is described. It is further shown how the devices could be configured so that addition and subtraction of positive and negative analog conductances could be performed. The presented memory structure requires a memristor model with a nonlinear programming sensitivity (programming threshold) for proper programming selectivity. A model of such a memristor is shown and key simulations are presented.

CIRCUIT MIMICKING TiO2 MEMRISTOR: A PLUG AND PLAY KIT TO UNDERSTAND THE FOURTH PASSIVE ELEMENT

Abstract: A plug-and-play kit that can be used as a teaching aid in high school has been designed, which mimics the behavior of recently discovered TiO2 based memristor. The circuit uses easily available off-the-shelf components to emulate a memristor. SPICE simulations and lab results are shown to validate the proposed circuit.

Compact model of memristors and its application in computing systems

Abstract: In this paper, we present a compact model of the spintronic memristor based on the magnetic-domain-wall motion mechanism for circuit design. Our model also takes into account the variations of material parameters and fabrication process, which significantly affects the actual electrical characteristics of a memristor in nano-scale technologies. Our proposed model can be easily implemented by Verilog-A languages and compatible to SPICE-based simulation. Based on our model, we also show some potential applications of memristor in computing system, including the detailed analysis and optimizations based on our proposed model.

Overview: Memristive devices, circuits and systems

Abstract: With conventional CMOS technology approaching fundamental scaling limits, novel nanotechnologies offer great promise for VLSI integration at nanometer scales. The memristor, or "memory resistor," is a novel nanoelectronic device that holds great promise for emerging VLSI applications. Essentially, a memristor is a programmable resistor whose resistance is altered based on specified toggle conditions. Furthermore, memristors are non-volatile such that the state of the device remains until the next toggle condition. This paper will provide an overview of memristors and memristive systems with a particular focus on applications for emerging VLSI circuits and systems. Examples of memristor based memory and logic circuits are to be discussed in detail including device modeling, memristor memory analysis, and memristor based logic. While the examples shown are focused on digital applications, memristors also hold great promise for analog, mixed signal and biomedical systems. These several potential applications will be discussed as part of this overview.

Bottleneck of using single memristor as a synapse and its solution

Abstract: Physical realization of the first memristor by researchers at Hewlett Packard (HP) labs attracts so much interest in this newly found circuit element which has so many applications specially in a field of neuromorphic systems Now, it is well known that one of the main applications of memristor is for the hardware implementation of synapses because of their capability in dense fabrication and acting as a perfect analog memory However, synapses in biological systems have this property that by progressing in the learning process, variation rate of the synapses weights should decrease which is not the case in the currently suggested memristor-based structures of neuromorphic systems In this paper, we show that using two dissimilar memristors connected in series as a synapse perform better than the single memristor

Memristive Systems Analysis of 3-Terminal Devices

Abstract: Memristive systems were proposed in 1976 by Leon Chua and Sung Mo Kang as a model for 2-terminal passive nonlinear dynamical systems which exhibit memory effects. Such systems were originally shown to be relevant to the modeling of action potentials in neurons in regards to the Hodgkin-Huxley model and, more recently, to the modeling of thin film materials such as TiO2-x proposed for non-volatile resistive memory. However, over the past 50 years a variety of 3-terminal non-passive dynamical devices have also been shown to exhibit memory effects similar to that predicted by the memristive system model. This article extends the original memristive systems framework to incorporate 3-terminal, non-passive devices and explains the applicability of such dynamic systems models to 1) the Widrow-Hoff memistor, 2) floating gate memory cells, and 3) nano-ionic FETs. Keywords-memristive systems, memistor, transconductance, synaptic transistor, non-linear dynamic systems

Memristor system properties and its design applications to circuits such as nonvolatile memristor memories

Abstract: Novel nonvolatile universal memory technology is essential for providing required storage for nano-computing. As a potential contender for the next-generation memory, the recently found “the missing fourth circuit element”, memristor, has drawn a great deal of research interests. In this paper, by starting from basic memristor device equations that assumes constant ion mobility, we develop a comprehensive set of properties and design equations for memristor based memories. Our analyses are specifically targeting key electrical memristor device characteristics relevant to, but not limited to, memory operations. However, like many nano devices, a small voltage drop across the memristor will yield an enormous electric field, which may produce significant highly nonlinear ionic transport that the linear drift assumption no longer holds for realistic memristors. Issues such as how to design circuits facing such nonlinear drift will be discussed. In addition, issues such as how to sense the memory states and perturbations during sensing will be addressed. In this paper, we demonstrate that we can successfully use the derived properties based on the linear drift model to design read and write circuits and analyze important data integrity and noise-tolerance issues for realistic nonlinear drift models.

A novel ferroelectric memristor enabling NAND-type analog memory characteristics

Abstract: Interfacial conduction had been confirmed at the surface of ferroelectric thin film owing to the extremely high charge density over 1014 cm−2 [1]. The effect is of interest because it may be used to make a unique memristor [2] (or memistor [3]). The nonvolatile nature of memristor makes it an attractive candidate for the next-generation memory technology. Recently, we have demonstrated the conductivity modulation of the interface between two oxides, ZnO and PZT, in a ferroelectric gate field-effect transistor (FeFET) [4,5], which is applicable for a nonvolatile memory. In this study, we demonstrate an Oxide Memory (OxiM) transistor as a new type of FeFET, provided with dual (top & bottom) gate, which can memorize the channel-conductance with the dynamic range over 105. By using serially-connected OxiM transistors, we were successful in fabricating NAND memory circuit with a retention time over 3.5 months. Since the ferroelectric polarization can be modulated continuously by the gate voltage, note that multi-valued data can be memorized in an OxiM transistor. This present new transistor is implemented by all oxide-based thin films, which include SrRuO 3 (SRO: bottom gate electrode), Pb(Zr,Ti)O 3 (PZT: ferroelectric), ZnO (semiconductor), and SiON (gate insulator).

The memristor as controller

Abstract: Recently a fourth circuit element, predicted four decades ago, has been discovered by HP researchers. This device, known as the memristor, is basically a resistance with memory that can be used as a tunable gain in control systems. In this paper the memristor experimental characteristic is modeled with a describing function and used to predict oscillations in closed loop systems with linear plants.

Spintronic devices: From memory to memristor

Abstract: In 1971, Professor Leon Chua in UC Berkeley predicted the fourth fundamental passive circuit element - memristor, based on the conceptual completeness of circuit theory. 37 years later, a team at HP Labs led by Dr. Stanley Williams announced the development of the first switching memristor. From then, more and more researches on memristor are conducted at various levels. Spintronic technology was introduced to the nonvolatile memory design regime in the recent decade. For example, spin-transfer torque random access memory (STT-RAM) has demonstrated many promising characteristics such as non-volatility, zero standby power, nanosecond access time, high memory density, and good scalability. In this paper, we will give a short tutorial of our works in STT-RAM from the viewpoints of device, design and system applications. On the top of that, we will also discuss one type of memsitors based on spintronic technology (spintronic memristor), including the device modeling and the applications in sensor.

A new modified nodal analysis for nano-scale memristor circuit simulation

Abstract: It is unclear how to include the newly discovered memristor together with traditional electronic devices into a circuit simulator such as SPICE. To perform a fast prototyping of circuits composed of memristors at nano-scale, this paper introduces a new modified nodal analysis (MNA) to include this fourth circuit element into a first-order differential-algebra-equation (DAE). In the new MNA, magnetic flux is employed as the state variable for a flux-controlled memristor, called memductor. The new MNA is implemented in a circuit simulator to efficiently provide time-domain transient simulations for a number of nano-scale memristor-based circuits.

Memristive systems analysis of 3-terminal devices

Abstract: Memristive systems were proposed in 1976 by Leon Chua and Sung Mo Kang as a model for 2-terminal passive nonlinear dynamical systems which exhibit memory effects. Such systems were originally shown to be relevant to the modeling of action potentials in neurons in regards to the Hodgkin-Huxley model and, more recently, to the modeling of thin film materials such as TiO 2−x proposed for non-volatile resistive memory. However, over the past 50 years a variety of 3-terminal non-passive dynamical devices have also been shown to exhibit memory effects similar to that predicted by the memristive system model. This article extends the original memristive systems framework to incorporate 3-terminal, non-passive devices and explains the applicability of such dynamic systems models to 1) the Widrow-Hoff memistor, 2) floating gate memory cells, and 3) nano-ionic FETs.

On the Discovery of a Polarity-Dependent Memory Switch and/or Memristor (Memory Resistor)

Abstract: In a recent editorial of IETE Technical Review, Jagadesh Kumar [1] has rightly pointed out the importance of a novel experimental device (a new passive circuit element apart from R, L, C) identified by Strukov et al. as a memristor (memory resistor). This was predicted by Chua [2] theoretically long back. The device is characterized by a Figure of eight (8)-type I-V characteristics as a consequence of the device resistance “remembering” the last current (or charge) passed through it. Strukov et al. [3] emphasized the use of a nano-semiconductor (TiO2) for attaining this characteristic, where the resistance of TiO2 could be modulated by superimposing O22 ionic transport which can be stopped as such after the removal of voltage (so as to remember the charge transport). This is the basis of its memristor-type behavior. The purpose of this note is to point out that such an experimental device (termed as polarity-dependent memory switch) had already been reported in mid-90s by our group in India [4], which Strukov et al. missed to mention in their paper (private communication with the senior author Dr. R. S. Williams [3]). We had clearly reported the basic important features which Strukov et al. reported only recently, namely, (a) a figure of “8”-type I-V characteristics akin to a memory switch; (b) hysteresis at the initial stage of the making of the device; (c) retention of “OFF” as well as “ON” states for many days; and (d) invoking the concept of superposition of ionic transport and electron transport to explain the memory effect. We had given a detailed phenomenological explanation while Strukov et al. have given an analytical model.

Memristors and crossbar latches

Abstract: The Memristor is believed to be the missing 4th circuit element. Memristor is basically a charge-dependent resistor. The reason that the memristor is radically different from the other fundamental circuit elements is that, unlike them, it carries a memory of its past. When you turn off the voltage to the circuit, the memristor still remembers how much was applied before and for how long. That's an effect that can't be duplicated by any circuit combination of resistors, capacitors, and inductors, which is why the memristor qualifies as a fundamental circuit element. Memristors can be combined into devices called crossbar latches, which could replace transistors in future computers, taking up a much smaller area. They can also be fashioned into non-volatile solid-state memory, which would allow data density of about 100GB/1sqcm. This can be implemented for designing circuits with lesser components, lesser expenses and lesser power consumption. Also coupling the crossbar latch with FPGA (Field Processing Gate Array) technology, we can potentially make processors so dynamic that they would never get obsolete. Giving a practical solution to reduce the millions of tonnes of computer waste generated each year...

A multivalued storage system using memristor

Abstract: For many years the only known passive circuit elements were resistor, inductor and capacitor. In 1971, Leon Chua showed using argument that there should exist another passive element which he named memristor. It is basically a resistor whose resistance increases when current flows through it from one direction and decreases when current flows from the other direction. After 37 years researchers of HP became able to build world's first working memristor and surprised the electronics community. Chua proved that the characteristics of a memristor cannot be simulated using resistor, capacitor and inductor only and hence it is a fundamental element. Many new types of circuits can be built using memristor in it. But as it is a very new element so the no. of circuits is only a few. As memristor can have many resistance levels, we can use some discrete value as different logic level and thus can use in multivalued logic system. In this paper a method has been shown to achieve those different levels. Using this method we can use an array of memristor for making a non-volatile multivalued data storage system‥